Cannot access class methods via generics

问题

I changed my method to generic method. What is happening now is that I was deserializing the class inside the methodB and accessing its methods which I can not do anymore.

<T> void methodB(Class<T> clazz) {
    T var;
    HashMap<String, T> hash = new HashMap<>();
}

void methodA () {
  methodB(classA.class);
}

Initially inside methodB with no generics,

var = mapper.convertValue(iter.next(), ClassA.class);
var.blah() //works fine

After using generics,

var = mapper.convertValue(iter.next(), clazz);
var.blah() //cannot resolve the method.

How do I access blah() method of classA?

回答1:

I think you should use interfaces instead of generics, if you want to call the same 'blah' function on a variety of classes (A,X,Y,Z) (each of which has the same function signature)..

Your other option (if you cannot modify A, e.t.c) is to use reflection. read more about this in https://docs.oracle.com/javase/tutorial/reflect/

回答2:

Thanks to Passing a class with type parameter as type parameter for generic method in Java. Solved using TypeToken

回答3:

The line where you assign to var at runtime is absolutely irrelevant. The only thing that matters for compiling a call is the static (compile-time) type of var. Since T is unbounded (other than by Object), it is not known to support any methods, other than those provided by Object. Both pieces of code should fail to compile.

来源：https://stackoverflow.com/questions/27413818/cannot-access-class-methods-via-generics